Wednesday, May 8, 2013

Two Maps That Explain VA's Changing Electorate

Cartograms are an effective way to project data, especially when the values of a given variable are extremely disproportionate. You've probably seen cartograms before: the area of polygons are distorted to a ratio of some other variable. They've been around since the 19th century, and a classic one is the U.S. states distorted to reflect their populations.

Dr. Stephen Farnsworth, a former professor of mine at the University of Mary Washington, sent me some very interesting cartograms that visualize his analysis of population change in Virginia, a favorite topic here at Map Attacks. Dr. Farnsworth and his colleague across the hall in the geography department, Dr. Stephen Hanna, published the report on the changing Virginia lanscape electorate in the Virginia News Letter last week.

Here's a typical, static map of Obama's performance by county in Virginia in 2012.

Fine. Makes sense. Democrats in the D.C. suburbs and southeast, Republican strongholds in southwest and pretty strong in the central areas except for Richmond. But Virginia has two Democratic Senators and Obama won twice. The solution to this cognitive dissonance of course is that not all counties are created equal. So redraw the area of the county polygons to reflect population, and you get a much better idea of what's going on:

An even stronger visual of what's going on in Virginia politics is seen here, in a cartogram of the increase in percent of votes cast for each candidate:

Stay tuned for some new cartograms about Washington: Crime, population size, and median income will be the usual suspects, but if there's anything you'd like to see, especially something that might tell a different story than just "Northwest is rich and safe and Southwest is poor and dangerous," let me know and I'll do my best to accommodate.

I also recommend everyone check out Hanna and Farnsworth's full report here: